Offset printing presses require very close synchronization of their gear trains in order to obtain satisfactory prints. A small amount of backlash or out-of-true running is enough to affect the quality of the prints. To synchronize the gearwheels, it is known in the prior art that means can be provided for radially deforming a gear rim so that it properly meshes with the adjacent gearwheel.
For example, DE-PS 1 650 784 discloses two variants of tensioning means for subjecting the gear rim of the drive gear of an offset press cylinder to radial deformation. In one of these variants, the gearwheel can be subjected to radial deformation from the force of an axially adjustable wedge disposed in an axial bore in the rim of the gearwheel. Alternatively, a radially disposed adjustable screw can be located in an axial bore. However, even if the bores are made relatively large, the tensioning devices lift only a few teeth of the gearwheel. As a result, therefore, these tensioning means produce undesirable gear impacts because there is only local deformation at one circumferential location of the gear rim.
In another prior art arrangement, DE-PS 2 829 026 discloses a gear drive in which the helical spur gearwheels have a coaxial tensioning disk. As disclosed in this reference, each tensioning disk has two or more tensioning devices which act axially on the rim of the gearwheel and the elastic axial deformation of the helical gear rim is used to adjust the backlash. Here, however, the gear teeth are tilted somewhat during the axial deformation produced by the tensioning disk.